1. Field of the Invention
This invention relates generally to systems for controlling the weaving of chain link fence, and more particularly, to an improved and simplified system for controlling a chain link fence weaving machine and for weaving the fence.
2. Description of Related Art
Chain link fence weaving machines are well known in the art. One example of a single wire prior art chain link weaving machine, is shown in U.S. Pat. No. 1,005,480 to Schmid. This patent discloses a machine having a knife or weaving blade which bent a single strand of wire into a zigzag configuration now referred to as a "needle". The needle is passed through a feed into a spiral gripper or plaiting tube where the single needle is woven to a fence portion held in the spiral gripper. The plaiting tube and/or spiral gripper is now referred to in the art as a "trough". Many improvements have been made in chain link fence weaving machines since the issuance of the Schmid patent, however the trough still remained tubular. For example, a more recent improvement in chain link fence weaving machines is the 2MT-VS, variable drive automatic fence weaving machine manufactured and sold by BMCI, Inc., doing business as Bergandi Machinery Company of South El Monte, Calif. The Bergandi machine is commonly referred to as an automatic two (2) wire type, wherein two strands of wire from two large coils of wire are continuously fed onto a forming mechanism (weaving blade), so that two needles at a time are formed into a picket in an intercoiled manner and then woven by a trough weaving mechanism to form continuous lengths of chain link. An example of such 2 wire weaving machines is disclosed in U.S. Pat. No. 4,566,501 to Rohrbacher.
In the 2 wire prior art machines a main spindle shaft drives a weaving blade that coils the 2 strands of wire to form a picket. The main spindle shaft and attached weaving blade must be repeatedly stopped and started at precise intervals to allow for picket cutting, indexing and selvage, and the subsequent weaving of the picket into the formed fence. In addition to stopping at a precise point, the main spindle shaft must be prevented from counter-rotating, when the picket on the weaving blade attempts to straighten itself out. Additionally, when the 2 intercoiled needles are cut on 2 wire machines, such as the Bergandi machine, the cutting mechanism forms a hook, referred to as the "starting hook" on the cut off end of one of the needles. The needle having the starting hook formed thereon is referred to as the "leading needle or wire", and is the needle that is actually woven to the previously woven fence in the trough. The second needle is referred to as the trailing needle, and as described above, is intercoiled with the leading needle to form a picket.
The required starting, stopping and indexing of the main spindle shaft of prior art machines, such as the Schmid and Bergandi weaving machines mentioned above, are normally controlled with mechanical or electro-mechanical clutch-brake type mechanisms. These mechanisms are typically coupled between the main spindle shaft and a main motor or prime mover of the weaving machine. The clutch-brake mechanism is usually activated by a signal received from a control mechanism, which in present day machines may be a digital counter. After an activation signal is received by the mechanism, the motor is disconnected from the system through the clutch and the main spindle shaft is stopped and held by the brake device. Such clutch-brake mechanisms take many well known configurations, such as friction clutch-hydraulic brake devices with positive stop, oil shear devices, and electro-mechanical devices.
A disadvantage of the known clutch-brake devices, is that the motor continues to operate at a fixed speed, while it is disconnected from the system, since it is mechanically disconnected by the clutch. The output rate of the known weaving machines are controlled by the speed of the spindle, approximately 600 RPM, and such weaving machines are limited to the clutch-brake mechanism's ability to control the torque that the motor is generating at the fixed speed. Therefore, the output rate of such weaving machines is limited. A further disadvantage of clutch-brake mechanisms, is that when they are engaged to start weaving further pickets to a fence, a "fast start" occurs when the motor operating at its fixed speed is engaged. When the motor is so engaged, depending on the gauge of the wire and the speed of the motor, the inertia of the wire wrapped around the weaving blade may cause the weaving blade to deform or abrade the wire and/or, may also bend the starting hook, causing it to misweave. In addition to abrading the wire and bending the starting hook, this fast start causes stress to the weaving blade. These abrading and bending problems are a particularly serious problem if higher speeds are attempted, when using lighter gauge wires, and/or when weaving PVC coated wires. A still further disadvantage of known clutch-brake systems, is that they do not stop the main spindle shaft at precise intervals, so that indexing for the weaving of the next picket to be woven is somewhat inefficient. Another disadvantage of clutch-brake mechanisms, is that they may fail over time, due to wear, for example.
A further disadvantage of the prior art has recently been discovered when control means, such as disclosed herein, allowed increased production rates of chain link weaving machines. At such increased production rates, the starting hook of the leading needle, which is being rotated in the known troughs, tend to catch in the holding slot of the troughs, since the starting hook is spiraling through the trough at higher speeds. When a starting hook catches in the slot, it deflects and causes a misweave of the fence. Additionally, at higher weaving speeds, the starting hook of the leading needle may flex, so as to not initially enter a previously woven picket, thereby causing a misweave.
There is, therefore, a need for an improved and simplified chain link fence weaving machine that will operate at increased speed, and which includes a system for controlling the increased production rate, while at the same time preventing misweaves by such a machine.